Silicone foam-forming compositions and silicone foams made therefrom

Abstract

Silicone foam-forming compositions are disclosed that enable the production of silicone foams having densities <3 lbs/ft 3 and as low as 2.0 lbs/ft 3 or lower. The compositions comprise methyl hydrogen siloxane, one or more silanols that react with the methyl hydrogen siloxane in the presence of a platinum group catalyst, a long chain alcohol having between 5 and 12 carbon atoms, and starch. The silicone foams resulting from the foam-forming compositions are mechanically stable (non-friable) and do not collapse.

1 . A silicone foam-forming composition comprising:
 (a) at least one methyl hydrogen polysiloxane having reactive hydrogens;   (b) optionally, from 0% to about 40% by weight, based on the total weight of the composition, of one or more supplemental blowing agents;   (c) a silanol component comprising one or more silanols having reactive hydroxyl groups;   (d) at least one long-chain alcohol having a carbon chain length in the range of 5 to 12 carbon atoms and reactive hydroxyl groups;   (e) optionally, from 0% to about 49% by weight, based on the total weight of the composition, of starch; and   (f) a catalyst suitable for catalyzing a reaction between the methyl hydrogen polysiloxane and the silanol component,   wherein the composition has a stoichiometric molar ratio of reactive hydrogens to total amount of reactive hydroxyls of 50:1 to 1:1.   
     
     
         2 . The composition of  claim 1 , wherein the methyl hydrogen polysiloxane is in an amount of 5% to 66% by weight, preferably 32%-44% by weight based on the total weight of the composition. 
     
     
         3 . The composition of  claim 1 , wherein the supplemental blowing agent is present in the composition in an amount of 0.5% by weight to 40% by weight, based on the total weight of the composition, preferably 0.5% to 11% by weight. 
     
     
         4 . The composition of  claim 1 , wherein the supplemental blowing agent is an aliphatic or cycloaliphatic blowing agent having from 4 to 7 carbon atoms, preferably pentane, and optionally has a boiling point of −20° C. to 70° C. 
     
     
         5 . The composition of  claim 1 , wherein the silanol component is in an amount of about 14% to about 80%, preferably about 14% to about 70% by weight based on the total weight of the composition. 
     
     
         6 . The composition of  claim 1 , wherein the silanol component comprises a blend of two or more silanol components, wherein the blend of silanol components comprises a low viscosity silanol having a viscosity of about 10 cP to about 100 cP, and a higher viscosity silanol having a viscosity of about 100 cP to about 2000 cP, wherein the low viscosity silanol is in an amount of about 6% to about 26% by weight, and the higher viscosity silanol is in an amount of about 8% to about 46% by weight, based on the total weight of the composition. 
     
     
         7 . The composition of  claim 6 , wherein the low viscosity silanol and the higher viscosity silanol are in a weight ratio of higher viscosity silanol to low viscosity silanol of about 6:1 to 1:3, preferably about 2:1. 
     
     
         8 . The composition of  claim 1 , wherein the long-chain alcohol is in an amount of about 3% to about 40% by weight, preferably about 3% to about 17% by weight, based on the total weight of the composition. 
     
     
         9 . The composition of  claim 1 , wherein the starch is in an amount of about 0.1% to about 49% by weight, preferably about 0.4% to about 17% by weight, based on the total weight of the composition, and optionally has a particle size in the range of about 1 micron to about 100 microns. 
     
     
         10 . The composition of  claim 1 , wherein the catalyst is a platinum-group catalyst in an amount of about 1 ppm to about 100 ppm, preferably 9 ppm to 74 ppm platinum-group metal, based on total weight of the composition. 
     
     
         11 . The composition of  claim 1 , wherein the composition is essentially free of mineral fillers. 
     
     
         12 . The composition of  claim 1 , wherein the composition is a 2-part composition having a first part and a second part, wherein the first part comprises:
 (i) the methyl hydrogen polysiloxane in an amount of 5% to 66% by weight, based on the total weight of the composition,   (ii) optionally up to 100% of the amount of supplemental blowing agent,   (iii) optionally up to 100% of the amount of the silanol component,   (iv) optionally up to 100% of the amount of the long-chain alcohol, and   (v) optionally up to 100% of the amount of the starch, and   wherein the second part comprises:
 (i) the catalyst in an amount of 1 ppm to about 100 ppm, 
 (ii) optionally up to 100% of the amount of supplemental blowing agent, 
 (iii) optionally up to 100% of the amount of the silanol component, 
 (iv) optionally up to 100% of the amount of the long-chain alcohol, and 
 (v) optionally up to 100% of the amount of the starch, 
 with the proviso that the silanol component, the long-chain alcohol, the supplemental blowing agent, when present, and the starch, when present, are contained in at least one of the first part or the second part. 
   
     
     
         13 . The composition of  claim 12 , wherein the first part comprises the methyl hydrogen polysiloxane and the supplemental blowing agent, and the second part comprises the silanol component, the long-chain alcohol, the starch, and the catalyst. 
     
     
         14 . The composition of  claim 13 , wherein first part has a viscosity of about 0.5 to about 100 cP at 25° C., preferably about 1 to about 40 cP at 25° C., more preferably about 10 to about 20 cP at 25° C., and wherein the second part has a total viscosity of about 0.5 to about 1000 cP at 25° C., preferably about 1 to about 600 cP at 25° C., more preferably about 100 to about 400 cP at 25° C. 
     
     
         15 . A silicone foam formed from the silicone foam-forming composition of  claim 1 , wherein the silicone foam has a density of less than 5 lb/ft 3  or less, preferably 3 lb/ft 3  or less. 
     
     
         16 . The silicone foam of  claim 15 , wherein the foam is an open cell foam, a spray foam, a pour-in-place foam, or a froth pack foam. 
     
     
         17 . A method for preparing a silicone foam comprising:
 (1) providing
 (a) at least one methyl hydrogen polysiloxane having reactive hydrogens; 
 (b) a silanol component comprising one or more silanols having reactive hydroxyl groups; 
 (c) at least one long-chain alcohol having a carbon chain length in the range of 5 to 12 carbon atoms and reactive hydroxyl groups; 
 (d) optionally, starch; 
 (e) a catalyst suitable for catalyzing a reaction between the methyl hydrogen polysiloxane and the silanol component; and 
 (f) optionally, one or more supplemental blowing agents other than a long-chain alcohol; and 
   (2) combining and reacting, under suitable reaction conditions, components (a) through (f) to form the silicone foam, wherein the components are combined such that reactive hydrogens from the methyl hydrogen polysiloxane, and reactive hydroxyl groups from the silanol component and the long-chain alcohol, are at a stoichiometric ratio of 50:1 to 1:1.   
     
     
         18 . The method of  claim 17 , wherein the method comprises providing a first part comprising the methyl hydrogen polysiloxane and optionally, the supplemental blowing agent, and a second part comprising the silanol component, the long-chain alcohol, the starch, and the catalyst. 
     
     
         19 . The method of  claim 18 , wherein first part and the second part are combined and reacted by spraying the first part and the second part together, optionally wherein the spraying occurs at a pressure of about 10 psi to about 900 psi. 
     
     
         20 . The method of  claim 18 , wherein the first part and the second part are combined and reacted by mixing the first part and the second part together in a pre-made form.